In a field sequential LCD, a pixel is sequentially illuminated with red light, green light, and blue light during one frame. In a typical thin film transistor (TFT) LCD, one pixel having three sub-pixels of red (R), green (G), and blue (B) displays an image containing the three colors simultaneously in one frame. In the field sequential LCD, unlike the TFT LCD, one pixel displays images of R, G and B in sequence during one frame.
Accordingly, the field sequential LCD does not necessarily include a color filter and displays an image having relatively high resolution compared with the TFT LCD. To perform a field sequential operation, one frame is divided into three sub-frames. That is, each frame is composed of a red field, a green field, and a blue field.
Each field has a reset period and a data programming period. During the reset period, a liquid crystal is initialized. During the data programming period, a data signal is applied to the initialized liquid crystal and the liquid crystal aligned in response to the data signal is illuminated with light. During the reset period, a reset signal is applied to the liquid crystal. The reset signal has a square pulse or square wave form.
FIG. 1 is a timing diagram illustrating a method of resetting a conventional field sequential LCD. Referring to FIG. 1, a frame is divided into three fields, e.g., into a red field, a green field and a blue field. Each field includes a reset period and a data programming period. For example, the red field includes a reset period and a data programming period. During the reset period, the voltage level of the reset signal applied to a corresponding pixel is equal to the voltage level of the data signal to be applied during the data programming period. Therefore, the pixel receives a square wave reset signal having a level of ΔV during the reset period.
However, the field sequential LCD does not have sufficient margin for the reset period, as compared with the TFT-LCD. Because one frame of the field sequential LCD has three fields and each field has a reset period and a data programming period, the reset period of the field sequential LCD is shorter than that of the TFT-LCD which resets only once per frame.
Further, the reset signal has the same voltage level as the data signal, therefore, the liquid crystal is not completely initialized. For example, when the liquid crystal has a relatively high transmittance by the data signal applied during a previous field, the transmittance of the liquid crystal should be lowered relatively more to initialize the liquid crystal during a current field. Here, the initialization of the liquid crystal depends on both the voltage level of the reset signal and the applied duration of the reset signal. Therefore, when the liquid crystal has a relatively high transmittance in the previous field, the liquid crystal is not completely initialized.